New sand poses possible threat to Tijuana River

Officials at Tijuana River reserve prepare for worst in wake of replenishment project in Imperial Beach

With Tijuana landmarks in the distance a man strolls beside the Tijuana Estuary near where it empties into the ocean. New sand on Imperial Beach is migrating south and threatens to close the mouth of the estuary.
— Bill Wechter / UT San Diego

With Tijuana landmarks in the distance a man strolls beside the Tijuana Estuary near where it empties into the ocean. New sand on Imperial Beach is migrating south and threatens to close the mouth of the estuary.
— Bill Wechter / UT San Diego

IMPERIAL BEACH  While some residents fight to stay afloat after a recent sand replenishment project in Imperial Beach went awry, the keepers of the Tijuana estuary prepare to keep the waters flowing at the river’s mouth.

The sand has not yet closed off the estuary, and it might not ever do so, but reserve manager Brian Collins said he and his team are preparing for the worst at the Tijuana River Estuarine Research Reserve.

“We do have concerns,” Collins said of the 450,000 cubic yards of sand that SANDAG deposited on the beach between September and October. Much of that sand has since been swept from the shore and migrated south toward where the estuary runs out to sea.

“It hasn’t behaved well, let’s put it that way,” Collins said.

He worries about what he calls the tidal prism, which is the volume of water that is able to leave the estuary at low tide. The water needs to flow freely in order to maintain the delicate ecosystem inside the reserve. Its flow, already threatened by debris from human activities upstream, now faces a new threat: potential closure from a sandbar at its outlet to the ocean.

The last time the river mouth closed completely was in the 1980s, he said, and it stayed closed for nine months. During that time, the water in the estuary became hyper-saline, causing plants in the marsh to die, and the population of light-footed clapper rails crashed because the marsh-dwelling birds were exposed to unusual predators.

Maintaining the ecosystem in the reserve takes a lot of attention, Collins said, and this potential sand plug is just one more thing to pay attention to.

“We don’t have an emergency, but we have a condition where we’re trying to keep an eye on it,” he explained. “Superficially, there appears to be a lot more material and sediment around the mouth with this additional new load.”

This is the time of year that closures typically happen, he added. The last time the estuary entrance was pinched off, in 2010, it closed only partially. Reopening it took several days, permits from several agencies, and $20,000. He isn’t sure how much it would cost to reopen the river if it is closed again. But he is sure he doesn’t have the budget for it, and he knows the state Department of Parks and Recreation doesn’t have it either.

“A storm at the wrong time in the wrong direction could close the mouth and that would be that,” Collins said.

That is not to say there would be no hope, if the river mouth did close. Collins and his colleagues have been working with regulators to prepare for the worst-case scenario and expedite approval for remediation.

“We’ve tried to prime the pump, so to speak, of our regulatory relationships so we can move the sand if we need to here in the future.

“The bottom line is, we’re trying to help manage this ecosystem as optimally as we can, and it needs a little help now because humans have messed up the watershed.”

Conservationists at Imperial Beach-based WiLDCOAST are worried about how the sand replenishment is affecting not only the estuary’s ecosystem, but also the nearby marine life and reef.

While residents expressed concern about private property damage from flooding caused by the sand project, WiLDCOAST Executive Director Serge Dedina said it is damaging public property, too.

“I am very concerned about the closure of the estuary, and we need to work with the managers to find out what is going to happen in that case,” he told council members. “That would be an ecological catastrophe.”

He called on city leaders to take charge of what happens on Imperial Beach’s shoreline, instead of letting SANDAG decide its destiny.

Meanwhile, he said, he is pleased the city has asked SANDAG to meet in February and discuss environmental impacts the project has had on the area.